1. Field of the Invention
The present invention relates to spherical bearings, having a ball or inner race that is pivoted for rotation in a static member forming a socket or outer race, and more particularly, to an improvement in such bearings that includes a "self-actuation" system provided internally thereof for deflecting the ball for rotation in a single plane, or if desired, in more than one place, as in a universal joint. The invention has especial utility for turning, or vectoring, the thrust produced by the propulsion system of a rocket propelled vehicle to change the direction of flight.
2. Description of the Prior Art
Thrust vector control systems for rocket propelled vehicles are known in the prior art in which the nozzle, including the nozzle throat and expansion cone, are pivoted, being carried by a spherical bearing, so that the rocket motor can be deflected to steer the vehicle.
Systems of this type including hydraulic cylinders that are positioned externally of the nozzle for deflecting the nozzle to change the direction of flight of the vehicle are disclosed in U.S. Pat. No. 3,049,877 granted to A. Sherman on Aug. 21, 1962 and U.S. Pat. No. 3,230,708 granted to D. H. Huang et al on Jan. 25, 1966, both of which patents are assigned to the assignee of the present invention. Such externally actuated thrust vector control systems are subject to a number of disadvantages from the standpoints of cost, weight, high actuation requirements, difficulty in packaging within the envelope of the rocket motor, and mechanical complication.
A thrust vector control system in which the nozzle is carried by the ball or race of a spherical bearing, and which includes a "self-actuation" or an internal actuation system for deflecting the nozzle to steer the vehicle, is disclosed in my U.S. Pat. No. 3,912,172 granted Oct. 14, 1975, and also assigned to the assignee of the present invention. The internal actuation system there disclosed includes a kidney shaped loop seal as an actuator in each quadrant of the spherical bearing, a flat tension band of stainless steel being provided around the entire perimeter of each kidney seal. Each kidney seal is captured, in its individual quadrant, within an annular chamber or space that is provided externally of the bearing outer race or socket, between a fixed wall on an external surface of the static member forming the socket, and a movable wall that is formed by the facing edge of an actuator concentric shell portion or actuator ring that is mounted on and is fixedly attached to the nozzle, the actuator ring being disposed in slidable relation with the external surface of the member forming the socket. One side of each kidney seal abuts against the said external surface and the other side abuts against the movable wall on the actuator ring, the circular ends of each kidney seal being free to move as the ball is rotated in the socket. The kidney seal actuators may also be employed in each quadrant of the spherical bearing in order to provide the function of a double acting actuator. U.S. Pat. No. 3,912,172 also includes a pressurized lubrication system for the bearing to balance the pressure load on the nozzle joint by the combustion chamber pressure as the latter acts upon the projected area of the nozzle.
Primary advantages of the self-actuation or internal actuation system of U.S. Pat. No. 3,912,172, as compared with the externally actuated spherical bearings mentioned hereinbefore, are their compactness, simplicity, economy and lower actuation requirements.
It has been found, however, that the torque developed by internal actuators such as those disclosed in U.S. Pat. No. 3,912,172, with constant actuation pressure, is inversely proportional to the magnitude of the bearing rotation, that is to say, the magnitude of the angle through which the bearing is rotated. The maximum torque that can be developed with such internally actuated bearings, accordingly, is a function of bearing rotational design requirements. Therefore, it follows that a bearing of given envelope intended for 5 degrees of rotation will have "longer" kidney seals than a bearing proposed for 15 degrees of rotation; and the torque available to drive the 5 degree bearing will be much greater than that available to drive the 15 degree bearing.